Recently, wooden boards such as particle boards have been noticed as substitutes for plywood mainly composed of logs, and at present they are used in a wide variety of the fields as structural members such as floorings and wall materials, interior molding members such as door members, furniture materials, etc.
Usually, particle boards are obtained by forming a mat from a mixture of an adhesive and particles obtained by grinding wooden materials (including constructional wooden wastes, reclaimed materials, etc.) having an air dried specific gravity (specific gravity in the state of being stabilized with a moisture content of about 5-13% by subjecting to moisture conditioning at general temperature and humidity) of about 0.4-0.7 and then press the mat.
As a method for making particle boards, for example, Patent Document 1 discloses press, by usual method, particles having a specific gravity of 0.2 or less, such as balsa. Non-Patent Document 1 discloses a method of making particle boards by pressing particles of low specific gravity which are obtained from poplar of China growth and adjusted in moisture content. Furthermore, Non-Patent Document 2 discloses making particle boards by pressing a mat of low specific gravity obtained from balsa, apitong, etc. at various compression ratios (specific gravity of board/specific gravity of raw material).
Patent Document 1: JP-A-2001-293706
Non-Patent Document 1: Abstracts of the 49th Annual Meeting of the Japan Wood Research Society 1999, page 264
Non-Patent Document 2: Journal of the Japan Wood Research Society Vol. 33, No. 5, p. 385-392, 1987